Generating alternating currents.



No. 715,545. Patented Dec. 9, I902.

C. S. BRADLEY. GENERATING ALTEBNATING CUBRENTS.

r-Application filed June 22, 1898.)

(No Model.)

. y g Inventor x 03% MM W UNITED STATES PATENT OFFICE.

CHARLES S. BRADLEY, OE AVON, NEW YORK, ASSIGNOR TO THE GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

GENERATING ALTERNATING CURRENT S.

SPECIFICATION forming part of Letters Patent No. 715,545, dated December 9, 1902. Application filed Tune 22, 1896. Serial No. 596l4c24=i (N model.)

To (LZZ whom, it may concern:

Be itknown thatI, CHARLES S. BRADLEY, a citizen of the United States, and a resident of Avon, in the county of Livingston and State 5 of New York, have invented certain new and useful Improvements in Generating Alternating Currents, of which the following is a specification.

This invention relates to alternating-curto rent generators.

The object of the invention is to develop alternating currents of simple or polyphase character and of any desired rate of alternation by apparatus of more simple construction than that heretofore employed.

I carry out the invention by providing one element of the generator with a winding connected in'circuit with an electric condenser or several condensers and a switch for opening and closing the condenser-circuit and provide a cooperating element adapted to be driven by a prime mover. Either element may be provided with a generating circuit or winding for carrying current off to a work- 2 5 circuit. The rate of alternation may be varied by operating the prime mover at a constant speed and rendering the condenser or condensers adjustable to vary the resonant rate of electric vibration in the field-magnet 3o circuit, in which case the generating-winding will be wound upon the field-magnet, or the condensers may be adjusted fora definite con stant rate of electric vibration and the prime mover be varied in-speed, the generating-cir- 5 cuit being in such case wound upon the element which cooperates with the field-magnet. The terms field-magnet and armature are to be understood as the magnetizing and generating members, respectively, when such 40 terms are employed in this specification. In

one form of the invention both the field-magnet and the armature circuits are wound upon the same core, the cooperating element being in such case a closed-circuited winding in inductive relation to the field-magnet and movable relatively thereto. IVhen polyphase currents are to be generated, the connections with the magnetizing-circuit on the field-magnet will be such as to develop a rotary magnetic 5o field, and the relatively movable element should be operated at a speed above synchronism with the rate for which the condensercircuit is resonantly adjusted. The condense r-circuits are provided with a switch by which they may be opened or closed. When the generator is shut down, the condensercircuits are left open, and the remanent static charge they retain serves to furnish an initial charge to the field-magnet when the generator is again operated. Thus the necessity of an independent eXciter is avoided. If the period of inactivity of the generator should be so long as to permit too great dissipation of the condenser charge, it may be given an initial charge by any small source of alternating or vibratory currents.

In Figure 1 of the accompanying drawings is shown one form of the invention, the condenser being of constant value. In Fig. 2 the condenser is shown as variable. In Fig. 3 the currents are taken from the cooperating element of the generator instead of from the one in which the magnetizing-currents are used.

A represents a field-magnet provided with a polyphase winding in circuit with three condensers c c 0 In the circuit is a switch S, by which the field-magnetizing circuit may be closed or opened. M is a cooperating element of the generator, provided with a closed winding. (Shown in Figs. 1 and 2 as a simple squirrel-cage winding, well understood by those familiar with'the construction of alternating-current apparatus.) This element is shown provided with a driving pulley and belt 8 for connection with a prime mover and when operated at a speed above synchronism with the rate of electric vibration of the field-magnetizing circuit will generate currents in the circuit B having the same time period or rate 0 as the condenser-circuit and the electromotive force of whichwill depend upon the difference in speed of the rotary field developed by the condenser-circuits and the driven element of the generator. It will of course be 5 understood that it is the relative motion of the elements A and M which determines the question of generation of current and that thereforeM might be the fixed and A the movable element. When the switch S is closed, the remanent charge of the condensers furnishes an initial charge to the field-magnet A, and the element M being in motion this charge is immediately magnified by inductive reaction, and a rotary field is set up in A. The rate of travel of the field, and consequently the rate of alternation of the generated current, depends upon the relation of capacity and inductance in the condenser-circuits and may be made anything desired by properly proportioning the two factors. The rate of alternation is determined by the product of capacity and inductance, the capacity in microfarads multiplied by the inductance in henries being equal to twenty-five thousand three hundred divided by the square of the rate. When a variable rateis required, the capacity of the condenser or condensers may be made variable. Such an organization is shown in Fig. 2, where also a single-phase organization is shown, and the work-circuit is supplied directly from the magnetizing-winding. In this case the generator is started up by the prime mover and the switch closed, thus furnishing an initial magnetizing-current, and the condenseris then adjusted to a resonant rate of vibration, corresponding to the desired rate of alternation. The work-circuit may be derived from any symmetrically-distributed points of the winding, but are preferably taken 0% at points midway between the points of connection with the charging-circuit. Alternating currents may also be derived from the driven element, in which case it should be provided with a ring or drum winding and tapped at suitable points. Such an organization is shown in Fig. 3 at M.

A generator of the kind herein described is eminently adapted for high-speed prime movers, such as rotary engines and turbines, for the reason that the periodicity of the generated current is a difierential of two speedsone controlled by the prime mover and the other controlled by the resonant rate established by a condenser in a circuit in which it is included. Evidently, therefore, the speed of the prime mover must be the sum of the speeds of the rotary field established by the condenser and the driven element. When the machine is in action, the energy in the condenser-circuits is furnished independently from the driven element; but the period is determined by the condensers and will vary according to the relation of their capacity and the inductance of the machine.

No claim is herein made to the method of generating currents described, such matter being covered by requirement of the Patent Office in a pending application, which is a division hereof, Serial No. 104,286, filed April 23, 1902.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is

1. An alternating-current generator having a field-magnet circuit including a condenser, a switch for opening and closing the circuit, and a relatively movable cooperating element in inductive relation to the field-magnet.

2. An induction-generator comprising a closed-circuited power-driven member and a cooperating member having a magnetizingwinding in a circuit, including a condenser and a switch.

3. An alternating-currentgeneratorhaving a field-magnet provided with a rotary-field winding including a plurality of condensers in circuit, a switch for opening and closing the circuit, and a cooperating relatively movable element in inductive relation to the fieldmagnet.

4. An induction-generator comprising two relatively movable elements, one of which includes a condenser and a switch in its circuit.

5. The combination of an alternating-current generator having a condenser and a switch in its magnetizing-circuit ofa'work-circuit connecting with its generating-winding.

6. An alternating-currentgeneratorhaving a magnetizing-winding charged bya plurality of condensers, a switch in the condenser-circuits and apower-driven member in inductive relation to the magnetizing-winding.

In testimony whereof I have hereunto subscribed my name this 29th day of May, A. D.

CHARLES S. BRADLEY. Witnesses:

ROBT. H. READ, A. WRIGHT CHAPMAN. 

